In charged particle beam apparatuses including electron microscopes, such as a scanning electron microscope (SEM) and a transmission electron microscope (TEM), lenses using an electric field or magnetic field are necessarily used in order to focus the charged particle beam. In the electric field or magnetic field lens, various aberrations occur inevitably. Therefore, even if the charged particle beam is intended to be narrowed by increasing a reduction ratio, a spot diameter cannot be made small because of large aberrations; therefore, improvement in observation of a fine structure and in dimensional measurement accuracy or precision cannot be performed.
In the charged particle beam apparatus, in order to improve resolution, introduction of an aberration corrector is being advanced. This aberration corrector usually includes multipole lenses installed in a plurality of stages, and removes aberrations included in the charged particle beam passing through their insides by generating electric fields or magnetic fields in the multipole lenses.
Regarding this aberration corrector, for example, one that uses four stages of the multipole lenses is disclosed in the following Non-patent document 1.
Moreover, as a technology of detecting geometrical aberrations of the charged particle beam apparatus and correcting them, for example, there is a deconvolution technology disclosed in the following Patent document 1. This technology acquires beam profile data by acquiring a just-focused image and a plurality of defocused images, performing Fourier transformation on each of the pieces of image data, dividing the defocused image data being Fourier transformed by the just-focused image data being Fourier transformed, and performing inverse Fourier transformation on this value. Then, various kinds of geometrical aberrations are found based on this beam profile data, and the various kinds of aberrations are removed by making the aberration corrector operate according to respective aberration quantities.
In the following Patent document 2, a technology of measuring aberrations is disclosed where, by controlling an aperture angle of incidence of the charged particle beam to a specimen, the geometrical aberrations of the second-order or higher are actualized.
The following Patent document 3 discloses a technology where the aperture has a plurality of openings as means for dividing an optical path of the primary charged particle beam into a plurality of optical paths, and chromatic aberration and the geometrical aberrations are corrected. The plurality of openings have a first opening placed on an optical-axis of the primary charged particle beam and a plurality of openings placed on one circumference centered on this first opening in an annular shape.